Integrator circuit for security validation



United States Patent 3,492,490 INTEGRATOR CIRCUIT FOR SECURITY VALIDATION Jack E. Bayha, Chesterland, and Kenneth T. Schrieber,

Bedford, Ohio, assignors to Transmarine Corporation,

Chesterland, Ohio, a corporation of Ohio Filed Dec. 19, 1966, Ser. No. 602,884 Int. Cl. G01n 21/30; G011 N32 US. Cl. 250-219 6 Claims ABSTRACT OF THE DISCLOSURE This invention relates to an integrator circuit for paper security or document validation.

Heretofore, it has been known to utilize a lined grid having spacing between adjacent lines thereof substantially equal in number and parallel to a portion of a document or security to be validated, whereby the detection of light passing through the grid and the security upon relative movement between the bill and the security in a direction substantially perpendicular to the direction of the lines of the grid will vary in intensity because alternating light-dark areas will occur thereby producing a pulsating electrical signal when such light is detected by a highly sensitive photocell. A solution to the problem of detecting a certain number of such pulsating signals with sufficient amplitude by a suitable integrating circuit which will operate reliably, and be of very low cost is needed to perfect the grid detection structure. The purpose of this invention is to provide such integration circuitry.

Therefore, the general object of the invention is to provide an integration circuitry for a plurality of pulsating signals to effect validation of a paper document which circuitry is extremely simple, highly effective, and very low cost.

A further object of the invention is to provide such circuitry for integrating or counting a number of electrical pulses having sufficient amplitude which utilizes the signal to drive an incandescent light bulb whereby the light bulb will not light unless a sufiicient number of pulses having sufiicient amplitude are present.

The aforesaid objects of the invention and other objects which will become apparent as the description proceeds are achieved by providing in an electrical circuit to achieve validation of a paper document the combination of a grid having a spacing between adjacent lines thereof substantially equal in number and parallel to a portion of the document, means to effect relative movement between the grid and the document in a direction substantially perpendicular to the direction of the adjacent lines of the grid, means to project propagating waves through the grid and the document and detect the intensity and variations in intensity passing therethrough to provide a sensing signal which is characterized by means to amplify the sensing signal, an incandescent electrical light bulb driven by the amplified sensing signal wherein re- 3,492,490 Patented Jan. 27, 1970 sistance of the bulb is preselected so as to be driven into incandescence by a sensing signal of predetermined qualities, and a photocell in substantially adjacent relation to the light bulb to sense when there is a predetermined amount of light emitted from the light bulb.

For a better understanding of the invention reference should be had to the accompanying drawings wherein:

FIG. 1 is a schematic block diagram illustrating the relationship of the electrical circuit or sensing module comprising the essence of the invention to an overall combination of bill validation equipment; and

FIG. 2 is an electrical schematic diagram of the circuitry contained in the sensing module of FIG. 1.

While it should be understood that the integration circuitry comprising the essence of the invention might be utilized for integrating practically any signal, it has been particularly designed to integrate a validation signal from a grid detection bill validating equipment such as illustrated and described in patent application Ser. No. 529,750, also assigned to Transmarine Corporation, Chesterland, Ohio. Thus, it is with this particular requirement in mind that the following description should be understood.

With reference to the general block diagram of FIG. 1, the grid detection system includes a light source 10 adapted to direct light through a grid 12, and a bill 14 or other document, to be validated, with the amount of light passing through the grid and bill being detected by a particular photocell detector 16. In utilizing a grid detection of this type, the grid 12 has a plurality of substantially parallel equally spaced lines which are of substantially the same number and spacing as the lines on some particular horizontal or vertical lines in the background of the portrait section of US. currency are suitable for this purpose. In order to achieve the objects of the grid validation technique, the bill 14 and grid 12 must be moved relative to each other at a minimum speed although the relative movement need not be uniform in a direction substantially perpendicular to the lines of the grid or the bill, respectively. In this manner, a very short distance of relative movement will achieve several alternating or pulsating light-dark areas because of the moire effect achieved by the successive alignment and misalignment of the closely and generally equally spaced lines of the grid and the bill. The photocell detector 16 senses the amount of light or propagating waves which pass through and wherein the amount of propagation naturally is controlled by the light-dark effects. Thus, the electrical signal detected by the photocell 16 is a pulsating signal having an amplitude and frequency which depends upon the particular characteristics of the document being tested, and upon whether it is genuine or not.

In actual practice, the invention contemplates that the light 10 emits waves in the infrared frequency range and visible light is filtered out by a suitable filter. In this instance, the photocell detector 16 will be only infrared sensitive, however, it will be very sensitive so as to closely and accurately detect the amount of wave propagation passing through the grid and bill so as to provide distinct and measurable differences between authentic and counterfeit or copies of the document to be tested.

In any event, the signal picked up by the photocell 16, which is an electrical signal, is sent into a sensing module, indicated generally by numeral 18, which circuitry comprises the essence of the invention, and will be more fully described hereinafter. The sensing module 18 in effect integrates the number of pulses and amplitude thereof detected by the photocell 16, and if a proper integration is obtained, a signal will be sent to the mechanism to withdraw the bill, indicated by block 20, with this mechanism then actuating a clearance sensing unit 22 to insure that the bill has been properly cleared, at which time a vend signal 24 will be emitted to dispense change, or other articles to be vended. Naturally, if the sensing module 18 does not detect a valid integration from the photocell 16, a reject signal 26 will be the resultant output.

For an understanding of the electrical structure of the sensing module 18, reference should be had to FIG. 2. Specifically, the module functions on the basis of a constant positive voltage source on line 30 and a negative return normally at ground on line 32. The photocell detector 16 is connected from the positive reference line 32 to a preselected input line 34. Thus, the voltage developed by the photocell 16 tends to charge a capacitor C1 with the pulsating signal developed thereacross. In effect, capacitor C1 passes the pulsating signal to the base of transistor Q1 to act as the drive or control current signal to transistor Q1 to elfect simple amplification thereof, in a manner well known by the art. To this end, the collector of Q1 is connected through resistor R1 to the positive reference line 30, while the emitter is connected through resistor R2 to the negative line 32. Thus, with the conduction of Q1 caused by the input drive signal on the base thereof through capaictor C1, the potential at point 40 on the collector side of Q1 beneath R1 will vary substantially in proportion to the input signal on the base from capacitor C1.

Then, in the usual manner to effect amplification with a transistor amplifier, the voltage fluctuation at point 40 causes a current fluctuation on the base of transistor Q2 to effect an amplification through Q2 of the original signal represented through capicitor C1. The collector of Q2 is connected through resistor R5 to positive potential 30 while the emitter is connected through resistors R6 and R7 to the negative potential 32. Again, the voltage potential at a point 42 in the collector line at the base of RS will be an amplified representation of the signal from capacitor C1. This signal is passed through a capacitor C4 and to the base of a transistor Q3 for further amplification. A resistor R8 is provided in this line to render Q3 nonconductive in absence of signal. The collector of Q3 is connected to positive line 30 through a transformer TR1 with the emitter of Q3 connected directly to negative line 32. Thus, it should be understood that the current passage through transformer TR1 dependent upon the amplification of all the transistors Q1, Q2, and Q3 will be an amplified duplication of the signal generated by photocell 16, with limiting features which follow.

A feedback circuit consisting of capacitors C2 and C3, and resistor R3 from the emitter of Q1 to the collector of Q2 is to do nothing more than eliminate undesired fre quencies in the signal and provide desired filter characteristics. In a similar manner, the line connecting the base of Q1 in effect to the negative reference potential 32 via resistor R4, and the R-C network consisting of resistor R7 and capacitor C5 is to stablize the DC bias conditions of Q1 and Q2.

In any event, it should be understood that the primary coil of the transformer TR1 is driven with a current signal to develop a voltage which is exactly corresponding proportionally to the varying voltage developed in detector 16 with modification created by the filtering. Thus, the secondary of transformer TR1 is connected directly to an incandescent electrical light bulb 44, but passing through a variable resistor VRI on one side thereof to allow a variable control to account for some change in the characteristics of bulb 44.

The energy generated upon amplification from the initial signal received from detector 16 is in effect utilized to drive the light bulb 44. The characteristics of bulb 44 are chosen as to its filament thermal inertia, and the necessary amount of current and time of current application required so that at least three (3) pulses of light-dark effects are seen by photocell detector 16 to drive the bulb 44 to incandescence, with each of these light-dark effects having a sufficient amplitude or difference between the amount of light seen when it is light and the amount when it is dark to meet a required minimum difference. Hence, the electrical energy generated in the secondary of transformer TR1 is absorbed by heating of the mass or filament of bulb 44, but must be of a sufficient signal to cause incandescence and the emission of photons or visible light from bulb 44.

As a means of detecting the emission of visible light, a photocell detector 46 is connected from positive reference line 30 to negative line 32 through a pair of resistors R9 and R10, and placed in close adjacent proximity to bulb 44. Naturally, with no light detected by detector 46, the voltage potential at a point 48 between resistors R9 and R10 will remain substantially constant. This potential is preselected so that a silicon controlled switch SCWl is not actua ed. However, when a resistance decrease is present in photocell detector 46, the potential at point 48 changes so as to cause actuation of SCWl to send a validated signal over a line 50, which signal goes on into the mechanism to withdraw, or accept the bill, as shown in block 20 of FIG. 1. The silicon controlled switch SCWl is connected between the positive reference line 30 and the negative line 32 through a resistor R11.

Thus, it should be understood that an integration of the pulsating signal as seen by detector 16 is achieved by utilizing this signal to drive an AC amplifier which terminates in an output transformer TR1, with such transformer driving an incandescent bulb whereby the bulb will become incandescent only upon a sufiicient drive signal representing at least 3 cycles or pulses from detector 16 which pulses have sufficient amplitude and frequency, The photocell detector 16 picking up the signals from the bill or grid system is preferably infrared sensitive and a very fast responsing photocell, whereas the photocell detector 46 is normally only sensitive to visible light and need not be of such great response or resolution since substantially any signal detected will cause ac uation of SCWI. This light-integrator circuit is basically a noise rejection circuit with good delay characteristics caused by the inherent properties necessary to heat the filament of an incandescent light bulb to incandescence so as to all w a proper integration to be sure a valid bill is present. Since the only light emitted which is visible by the entire validation operation is from bulb 44, and this can be from a very small Window on the bulb 44 to the very closely spaced adjacent photocell detector 46, the detection of the apparatus in operation cannot be achieved because no lights actually come on which are visible.

While no actual dimensions are considered critical in the adjacent spaced relationship between bulb 44 and detector 46, it is believed that approximately inch would conveniently meet the objects of the invention, but of course other variations above or below this figure and probably, changes in the characteristics of the bulb and detector, which achieve the principles desired would be effective.

While in accordance with the patent statutes, only one best known embodiment of the invention has been illustrated and described in detail, it is to be particularly understood that the invention is not limited thereto or thereby, but that the inventive scope is defined in the appended claims.

What is claimed is:

1. In a testing apparatus an electrical integrator to count a minimum number of substantially sinusoidal electrical pulses of a minimum peak to valley amplitude separation and a minimum frequency as determined by an object to be tested which is characterized by means to measure the peak to valley amplitude separation of the pulses,

means to electrically amplify the measured amplitude separation of the pulses,

an incandescent light bulb in circuit with said electrical amplifying means and receiving the pulses therefrom and having a filament of predetermined electrical resistance and thermal inertia characteristics to require the receipt of at least three pulses of minimum peak to valley amplitude separation and a minimum frequency to drive the filament to incandescence, and

means to detect when the filament becomes incandescent.

2. An apparatus as in claim 1 where means are connected to said detection means to provide a validation signal when said detection means are energized.

3. An apparatus according to claim 1 which includes a variable resistor connected in series with the filament of the light bulb to provide adjustability of the integrator to account for variables in the thermal inertia of the filament.

4. An apparatus to provide validation of a paper document with a grid having a spacing between adjacent lines thereof substantially equal in number and parallel to a portion of the document, means to effect relative movement between the grid and the document in a direction substantially perpendicular to the direction of the adjacent lines of the grid, means to project propagating waves through the grid and the document and detect the intensity and variations in intensity passing therethrough during the relative movement between the grid and the document to provide a sinusoidal sensing signal which is characterized by means to amplify the sensing signal,

means to effect signal feedback to eliminate undersirable signal frequencies and effect filtering,

an incandescent electrical light bulb driven by the amplified and filtered sensing signal, said bulb having a filament with a thermal inertia such that incandescence occurs only when the filament is driven by more than three sinusoidal pulses of the sensing signal of at least predetermined amplitude and frequency, and

a photocell in substantially adjacent relation to the light bulb to sense when the light bulb becomes incandescent and emits visible light.

5. An apparatus according to claim 4 wherein an AC transistor amplifier is utilized to amplify the sensing signal.

6. An apparatus according to claim 4 wherein the propagating waves through the grid and document are of infrared frequency, and the photocell detecting the visible light from the incandescent electrical light bulb is in such closely spaced and adjacent relationship that no visible light is emitted therefrom to any other parts of the apparatus.

References Cited UNITED STATES PATENTS 2,944,190 7/1960 Ost 250-205 X 3,014,134 12/1961 Bower 250237 X 3,293,656 12/1966 Blayney et al. 250-205 X 2,593,206 4/ 1952 Short.

3,094,617 6/ 1963 Humphries.

3,145,302 8/1964 Dunne et al.

3,151,281 9/1964 Kuehn 250-208 3,240,944 3/1966 Wolfson 250206 3,348,104 10/1967 Zielinski.

\VALTER STOLWEIN, Primary Examiner US. Cl. X.R. 250-205; 356-239 

